Abstract Several Piper species accumulate piperamides as secondary metabolites, and although they have relevant biological importance, many details of their biosynthetic pathways have not yet been described experimentally. Experiments involving enzymatic reactions and labeled precursor feeding were performed using the species Piper tuberculatum and Piper arboreum. The activities of the phenylalanine ammonia lyase (PAL) enzymes, which are involved in the general phenylpropanoid pathway, were monitored by the conversion of the amino acid L-phenylalanine to cinnamic acid. The activity of the 4-hydroxylase (C4H) enzyme was also observed in P. tuberculatum by converting cinnamic acid to p-coumaric acid. L-[UL-14C]-phenylalanine was fed into the leaves of P. tuberculatum and incorporated into piperine (1), 4,5-dihydropiperine (2), fagaramide (4), trans-piplartine (7), and dihydropiplartine (9). In P. arboreum, it was only incorporated into the piperamide 4,5-dihydropiperiline (3). L-[UL-14C]-lysine was successfully incorporated into the 4,5-dihydropiperine piperidine group (2), dihydropyridinone, and trans- (7) and cis-piplartine (8). These data corroborate the proposal of mixed biosynthetic origin of piperamides with the aromatic moiety originating from cinnamic acid (shikimic acid pathway) and key amide construction with amino acids as precursors.

Resumo Diversas espécies do gênero Piper acumulam piperamidas como metabólitos secundários e, embora tenham relevante importância biológica, detalhes de suas vias biossintéticas ainda não foram descritos experimentalmente. Experimentos envolvendo reações enzimáticas e incorporação de precursores marcados foram realizados utilizando as espécies Piper tuberculatum e Piper arboreum. As atividades das enzimas fenilalanina amônia liase (PAL), que estão envolvidas na via geral dos fenilpropanoides, foram monitoradas pela conversão do aminoácido L-fenilalanina em ácido cinâmico. A atividade da enzima 4-hidroxilase (C4H) também foi observada em P. tuberculatum pela conversão do ácido cinâmico em ácido p-cumárico. L-[UL-14C]-fenilalanina foi administrada em folhas de P. tuberculatum e incorporada em piperina (1), 4,5-di-hidropiperina (2), fagaramida (4), trans-piplartina (7) e diidropiplartina (9). Em P. arboreum, foi incorporado apenas à piperamida 4,5-dihidropiperilina (3). L-[UL-14C]-lisina foi incorporada com sucesso em 4,5-diidropiperina (2), trans-piplartina (7) e cis-piplartina (8). Esses dados corroboram a proposta de origem biossintética mista de piperamidas com a porção aromática originada do ácido cinâmico (via do ácido chiquímico) e construção de amida chave com aminoácidos como precursores.

Amides have been recognized as potent insecticidal natural products but, despite their variety of targets and mechanisms of action, their metabolic fate in insects is virtually unknown. The currently accepted hypothesis is that specialist herbivores are capable of biotransforming xenobiotics rendering them more polar and excretable while generalist insects do not have comparable capacity. The leaves from Piper tuberculatum, rich in insecticide amides, were offered to two insect species found on Piper leaves under natural conditions and also to four generalist grasshoppers in order to compare their capacity of biotransforming xenobiotics. The amides 1-7 were identified in the P. tuberculatum leaves and their corresponding carboxylic acids 8-13 were detected in frass samples of two host insects suggesting that these species promote the amides hydrolysis. The four generalist grasshoppers when offered P. tuberculatum leaves, starved to death after 72 h, indicating a strong antifeedant activity of P. tuberculatum leaves.

Piper gaudichaudianum Kunth (Piperaceae) accumulates gaudichaudianic acid, a prenylated benzopyran, as its major component. Interestingly, this trypanocidal compound occurs as a racemic mixture. Herein, transcriptomic investigations of Piper gaudichaudianum using the RNA-seq approach are reported, and from the analysis of the transcripts expressed it was possible to propose a complete biosynthetic pathway for the production of gaudichaudianic acid, including the steps that originate its precursor, p-hydroxybenzoic acid. Peperomia obtusifolia (L.) A. Dietr. (Piperaceae) also accumulates racemic benzopyrans, however, its chromanes originate from the polyketide pathway, while the chromenes from Piper derives from the shikimate pathway. Recent transcriptomic and proteomic studies of the former species did not identify polyketide synthases involved in the production of the benzopyran moiety, but revealed the expression of tocopherol cyclase, which may be responsible for the cyclization of the 3,4-dihydro-2H-pyran ring. The analysis of the enzymes involved in the secondary metabolism of Piper gaudichaudianum and the comparison with the data previously obtained from Peperomia obtusifolia can provide valuable information on how these compounds are biosynthesized.

Resumo Piper tuberculatum (Piperaceae) é uma espécie que acumula especialmente amidas como metabólitos secundários e diversas atividades biológicas dessa espécie foram relatadas anteriormente. No presente artigo, relatamos um estudo proteômico dessa espécie. Eletroforese bidimensional (2D SDS-PAGE) e espectrometria de massas (ESI-Q-TOF) foram utilizadas nesse estudos. Mais de cem spots e vários peptídeos foram identificados nesta espécie e as funções putativas desses peptídeos relacionadas a mecanismo de defesa como estresse biótico e abiótico foram atribuídos. As informações apresentadas ampliam a gama de informações moleculares dessa espécie.

Abstract Piper tuberculatum (Piperaceae) is a species that accumulates especially amides as secondary metabolites and several biological activities was previously reported. In this article, we report a proteomic study of P. tuberculatum. Bidimensional electrophoresis (2D SDS-PAGE) and mass spectrometry (ESI-Q-TOF) were used in this study. Over a hundred spots and various peptides were identified in this species and the putative functions of these peptides related to defense mechanism as biotic and abiotic stress were assigned. The information presented extend the range of molecular information of P. tuberculatum.

Dengue is a tropical disease caused by an arbovirus transmitted by Aedes aegypti. Since no effective vaccine is available for treating dengue, the present study focused on population vector control through investigating the use of the lignan grandisin, isolated from Piper solmsianum C. DC., Piperaceae, against the larvae of A. aegypti. Grandisin caused larval (L3) mortality at LC50 150 µg/mL. Histological analysis on A. aegypti larvae treated with grandisin (LC50 50 µg/mL) showed changes in the anterior-middle midgut, with intense tissue destruction and cell disorganization.

Um novo meroterpeno, 4-[(2'E)-3',7'-dimetilocta-2',6'-dienil]-5-metil-2-(3''-metilbut-2"‑enil)-benzeno-1,3-diol, além de oito substâncias conhecidas, foi isolado do extrato em MeOH das folhas de Peperomia oreophila Hesch. O fenol prenilado foi também isolado como principal componente do extrato em CH2Cl2:MeOH das folhas de Peperomia arifolia Miq. As estruturas das substâncias foram estabelecidas com base em dados espectrais e comparação com dados descritos na literatura

One new meroterpene, 4-[(2'E)-3',7'-dimethylocta-2',6'-dien-1'-yl]-5-methyl-2-(3"‑methylbut-2"-enyl)-benzene-1,3-diol, together with eight known compounds, was isolated from the MeOH extract from the leaves of Peperomia oreophila Hesch. The prenylated phenol was also isolated as main compound from the CH2Cl2:MeOH extract from leaves of Peperomia arifolia Miq. The structures of the substances were established on the basis of the spectral evidences and supported by literature data.

O perfil metabólito baseado na aplicação de análises multivariadas (análise de componentes principais, PCA) dos dados de espectrometria de massas com ionização electrospray (ESIMS) no modo positivo e de ressonância magnética nuclear (RMN) do ¹H de extratos brutos de espécies de Piper destacou algumas espécies caracterizadas pela produção de lignanas (P. solmsianum, P. truncatum e P. cernuum), neolignanas (P. regnellii) e cromenos (P. gaudichaudianum). Análises específicas em conjunto de espécies caracterizadas morfologicamente por apresentarem inflorescências pêndulas e globosas (P. caldense, P. carniconnectivum, P. bowiei e P. permucronatum) ou em espécies que produzem amidas indicaram o potencial mais significativo para tais análises como critério para estudos fitoquímicos posteriores. Análises intraespecíficas de plântulas das espécies P. solmsianum, P. regnellii e P. gaudichaudianum indicaram uma composição química nas folhas baseada na presença dos fenilpropanóides dilapiol e apiol, diferentemente do que produzem as plantas adultas. No caso das espécies que produzem amidas, a composição apresentou-se relativamente constante independentemente do estágio de desenvolvimento.

The metabolomic profiling based on the application of multivariate analysis (principal component analysis, PCA) of positive mode electrospray ionization mass spectrometric (ESIMS) and ¹H nuclear magnetic resonance (NMR) data of crude extracts highlighted some species characterized by lignans (P. solmsianum, P. truncatum and P. cernuum), neolignans (P. regnellii) and chromenes (P. gaudichaudianum). A specific analysis focusing on species having pendant and globular inflorescences (P. caldense, P. carniconnectivum, P. bowiei and P. permucronatum) or amides-producing species indicated higher potential of the methodology in determining similarities and establishing priorities for further phytochemical investigation. Such intraspecific analysis applied to analyzed seedling leaves of the P. solmsianum, P. regnellii and P. gaudichaudianum species revealed the production of dillapiole and apiole instead of lignans, neolignans or prenylated benzoic acid, produced by the adult leaves, respectively. In case of amides-producing species, a similar profile was observed regardless the developmental stage.

Extrato de folhas de Piper scutifolium apresentou atividade antifúngica significativa contra Cladosporium cladosporioides e C. sphaerospermum e seus principais componentes ativos, piperina, piperlonguminina e corcovadina foram isolados por meio de purificação biomonitorada, apresentando limites de detecção de 1 µg. Foi realizado um estudo da relação estrutura-atividade baseado na síntese de doze análogos com variações no número de insaturações, no padrão de substituição no anel aromático e no grupo amídico. As amidas sem substituintes no anel aromático e com apenas uma ligação dupla foram as mais ativas e os derivados N,N-dietil-substituídos apresentam maior dose-dependência.

The antifungal leaves extract from Piper scutifolium was submitted to bioactivity-guided chromatographic separation against Cladosporium cladosporioides and C. sphaerospermum yielding piperine, piperlonguminine and corcovadine as the active principles which displayed a detection limit of 1 µg. Structure-activity relationships were investigated with the preparation of twelve analogs having differences in the number of unsaturations, aromatic ring substituents and in the amide moiety. Analogs having a single double-bond and no substituent in the aromatic ring displayed higher activity, while N,N,-diethyl analogs displayed higher dose-dependent activity.

Piper tuberculatum Jacq. (Piperaceae) is used in traditional Peruvian medicine as anti-inflammatory and disinfectant of wounds in humans and domestic animals. This species contains amides bearing isobutyl, pyrrolidine, dihydropyridone and piperidine moieties. The aim of this work was to investigate antifungal activity of crude extracts from the spikes, leaves and stems of wild plants extracted with CH2Cl2:MeOH (2:1), EtOH, decoction, and in vitro plants extracted with CH2Cl2:MeOH (2:1). The crude extracts showed antifungal activity on Trichophyton rubrum, Mycosporum canis y M. gypseum. The minimum inhibitory concentration (MIC) observed with CH2Cl2:MeOH (2:1), EtOH and decoctions extracts against T. rubrum, M. canis and M. gypseum was 0,1 mg/mL for spikes and leaves, and 0,1 to 0,5 mg/mL for stems. The inhibition of growth using in vitro plants on T. rubrum and M. canis was 100% in 0,5 mg/mL, and 95% on M. gypseum 95% using 1,5 mg/mL of concentration.

En la medicina tradicional Peruana Piper tuberculatum Jacq. (Piperaceae) es utilizado en humanos y animales domésticos como antiinflamatorio y desinfectante de heridas. Piper tuberculatum contiene las amidas isobutílicas, pirrolidina, dihidropiridona y piperidina. El objetivo de este trabajo fue investigar la actividad antifúngica de los extractos crudos de inflorescencias, hojas y tallos de plantas silvestres, obtenidos con CH2Cl2:MeOH (2:1), EtOH y decocción y de plantas in vitro obtenido con CH2Cl2:MeOH (2:1). Los extractos crudos exhibieron actividad antifúngica sobre Trichophyton rubrum, Microsporum canis y M. gypseum. La concentración inhibitoria mínima (CIM) observada con los extractos CH2Cl2:MeOH (2:1), EtOH y decocción, sobre Trichophyton rubrum, Microsporum canis y M. gypseum fue 0,1 mg/mL para inflorescencias y hojas, y 0,1 a 0,5 mg/mL para tallos. En plantas in vitro la inhibición en el crecimiento de T. rubrum y M. canis fue 100% en 0,5 mg/mL y para M. gypseum fue 95% en 1,5 mg/mL de concentración.

The phytochemical investigation of Piper umbellata leaves yielded nine compounds including one terpenoid glucoside, five flavones (vitexin 2"-O-β-glucopyranoside, apigenin 8-C-β-D-glucopyranoside,orientin 8-C-β-D-glucopyranoside,5-hydroxy-7,3',4'-trimethoxy-flavone and velutin), two lignans (sesamin e dihydrocubebin) and 4-nerolidylcathecol. Excepting 4-nerolidylcathecol, all compounds have not been described from this species yet.

Bioguided fractionation of the extracts from leaves of Piper mollicomum and Piper lhotzkyanum against the fungi Cladosporium cladosporioides and C. sphaerospermum afforded seven bioactive compounds, four being chromenes: methyl 2,2-dimethyl-2H-chromene-6-carboxylate, methyl 8-hydroxy-2,2-dimethyl-2H-chromene-6-carboxylate, 2-methyl-2-[4'-methyl-3'-pentenyl]-2H-1-benzopyran-6-carboxylic acid, 2,2-dimethyl-2H-chromene-6-carboxylic acid, one a dihydrochalcone: 2',6'-dihydroxy-4'-methoxydihydrochalcone, and two flavanones: 7-methoxy-5,4'-dihydroxy-flavanone and 7,4'-dimethoxy-5-hydroxy-flavanone. The structures of the bioactive isolated derivatives were elucidated by interpretation of their NMR data [¹H and 13C (BBD, DEPT 135º)], and mass spectral data as well as by comparison with data described in the literature.

The composition of essential oils from leaves, stems and fruits of Piper aduncum, P. arboreum and P. tuberculatum was examined by means of GC-MS and antifungal assay. There was a predominance of monoterpenes in P. aduncum and P. tuberculatum and of sesquiterpenes in P. arboreum. P. aduncum showed the richest essential oil composition, including linalool. The essential oils from fruits of P. aduncum and P. tuberculatum showed the highest antifungal activity with the MIC of 10 µg as determined against Cladosporium cladosporioides and C. sphaerospermum, respectively. This is the first report of the composition of essential oils from P. tuberculatum.

O estudo fitoquímico biomonitorado do extrato em CH2Cl2 das folhas de Piper malacophyllum através da técnica de bioautografia frente a fungos, resultou no isolamento de dois piperolidos bioativos: 4,6-dimetóxi-5-E-fenilbutenolido (1) e 4,6-dimetóxi-5-Z-fenilbutenolido (2). Essas substâncias foram identificadas com base na análise dos espectros de IV, EM e RMN, incluindo técnicas bidimensionais, e comparação com dados descritos na literatura. A configuração E da ligação dupla confere maior atividade para 1 considerando-se que as quantidades mínimas de 1 e 2 necessária para inibir o crescimento dos fungos Cladosporium cladosporioides e C. sphaerospermum foram de 1,0/1,0 mig (1) e de 5,0/10,0 mig (2), respectivamente.

Bioactivity-guided fractionation of the CH2Cl2 extract from leaves of Piper malacophyllum using bioautography assay against fungi, led to the isolation of two known bioactive piperolides: 4,6-dimethoxy-5-E-phenylbutenolide (1) and 4,6-dimethoxy-5-Z-phenylbutenolide (2). IR, MS and NMR spectroscopic data were used for the identification of these compounds including comparison with previously reported data. The E configuration is associated to higher activity for compound 1, since the minimum amount required for the growth inhibition of Cladosporium cladosporioides and C. sphaerospermum were 1.0/1.0 mug (1) and 5.0/10.0 mug (2), respectively.